Heretofore, so-called stick-on-type disposable chemical warmers to be attached to a user's clothing or the like have been widely used. Such chemical warmers have a flat bag unit having an air-permeable surface and, inside the bag unit, an exothermic composition containing an oxidizable metal that generates heat upon contact with air (for example, see Patent Document 1). Stick-on-type disposable chemical warmers have an adhesive layer opposite the air-permeable surface of the bag unit. The adhesive layer enables the chemical warmer to be adhered onto the user's clothing or the like.